Original article
Fibrous cartilage in the rotator cuff: a pathogenetic mechanism of tendon tear?

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Abstract

There is no consensus on the pathogenesis of rotator cuff tears. Fibrous cartilage has been hypothesized to develop in some tendons as a result of shear or compressive forces, resulting in a tissue less capable of resisting normal tensile load and more prone to tearing. To test the hypothesis that metaplastic fibrocartilage in the rotator cuff could be involved in the pathogenic mechanism of its tear, samples from 34 acute and chronic torn rotator cuffs were subjected to histologic and immunohistologic study for the presence and type of cartilage (hyaline, fibrous, or elastic) in the area of the lesion and surrounding tissues. Detection of type I and II collagen, S-100 protein, and chondroitin sulfate allowed areas of fibrous cartilage to be seen in all samples, suggesting that the characteristic of rotator cuff tendons to work both in tension and in compression may stimulate fibrocartilaginous metaplasia and lead to a complete tear.

Section snippets

Patients and methods

Tissue samples of cuff tendons (collected more than 1 cm from the insertion) and adjacent bursa and deltoid muscle were obtained from 34 patients (24 men and 10 women), with a mean age of 60.5 years (range, 35-81 years), in the course of surgery for rotator cuff tear in 2000 to 2001. Lesions (both acute and chronic) were classified based on the Bernageau scale3: there were 15 grade I lesions (involving 1 tendon), 13 grade II lesions (involving 2 tendons), and 6 grade III lesions (involving 3

Histochemistry

All tendon fragments showed matrix disorganization, tissue necrosis, and fatty degeneration. Numerous areas of cartilage—detected at the edge of all tears—consisted of rounded cells surrounded by collagen fibers (Figure 1, Figure 2, A). These chondrocyte-like cells were either clustered in groups of 3 to 5 (Figure 3) or randomly dispersed in the matrix (Figure 4). Safranin O staining showed evident metachromasia of the cartilaginous matrix (Figure 1); the same cartilaginous areas also

Discussion

To our knowledge, this is the first study to report the presence and describe the type of cartilage in a substantial sample of torn rotator cuffs. Cartilage was detected in all of the tendon samples collected from adult patients with acute or chronic complete rotator cuff tears. Cartilaginous areas were consistently detected in the immediate vicinity of the tears but never at a distance from their margin or in surrounding bursa or muscle tissue. In these areas the tendons were not made up of

Acknowledgements

We are grateful to Ms Sandra Manzotti at the laboratory of the Department of Orthopedics, University of Ancona, Ancona, Italy, for the preparation of the histologic sections and to Dr Silvia Modena for reviewing the English.

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    Copyright © 2004 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.